What made Pakistan to think that India is their enemy just after the partition?

India being a Hindu majority country, in 1947, had adopted to be secular democratic and republic nation. On the other hand, Pakistan, led by Muhammed Ali Jinnah, opted to be a Islamic republic. The constant rivalry between Jinnah and Nehru in the years leading upto 1947 when the two nations became independent from the British rule, has led to view each other's nation with suspicion. Also, Pakistan chose to ally with USA, while India made friends with USSR. For a combination of reasons not limited to the above, Pakistan and India have remained enemies and will remain so.